I will attempt the impossible and try to explain paint without writing a book on the subject.
Basically there are 2 kinds of paint out there, ENAMEL and LACQUER. What are the differences and do you know which one you're getting?
To put it in the simplest terms, ENAMEL turns from soup to solid in TWO WAYS, evaporation of solvents AND a chemical reaction. The first part of the paint drying is the evaporation of solvents, but there is a lot more that has to happen within the paint before it is fully "cured" or hardened. After the solvets have evaprated, depending on the paint composition, the chemical structure undergoes a change by a variety of means which could be exposure to ultraviolet, exposure to oxygen, evaporation of a barrier chemical that prevents other components of the paint to cross link and harden in the can, exposure to heat and finally with paints that are formulated to do so, the addition of a catalyst or hardener. The hardening process can take as little as a few hours (typically paints that use a hardener such as epoxy or urethanes) to as long as months and sometimes even longer. Rustoleum is typical of an enamel that can take months to cure.
Once an enamel paint is cured, its chemistry has been changed which means it can no longer be dissolved by the solvents that you might have used to thin it down initially. This does not mean that the hard paint can not be attacked by solvents, but it does mean that the paint will not return to a liquid state. Maybe some kind of glop, but not liquid paint any more! Got that???
Now we come to LACQUER.
Lacquer does NOT change chemically when it dries. If you were to apply thinner to thoroughly dried lacquer, it would go right back to being liquid paint.
Now that you have a basic understanding about the differences, let's say you painted something with enamel (and we'll call it Rustoleum) and it's dry to the touch. You happen to smear it with some raw glow fuel and eventually you find the paint getting gummy and the color is wiping off. That's enamel that isn't fully cured! Remember, it could take months or longer to fully cure. Now let's say that a plane that was painted with Rustoleum sat around for years and suddenly you expose it to some glow fuel or some harsh solvent. I can promise you it will not get gummy, at least not without the added feature of the paint wrinkling up on the surface as if paint remover had been applied to it.
From my own observations, I find that although fully cured enamels generally have better chemical resistance than lacquers, lacquer has a tendency to dry faster and develop initial chemical resistance in a much shorter period of drying time.
Hopefully this has helped to clarify more than confuse, but I expect you get a little of both.
